1. Technical Field
The present invention generally relates to a digital image system which transmits digital image data, and more particularly, to a digital image system in a high definition multimedia interface (HDMI) format or a digital visual interface (DVI) format.
2. Background Art
Referring to FIG. 1, a digital image system in a basic high definition multimedia interface (HDMI) format includes a host device 11, a display device 12, and electric cables. The electric cables are connected between input/output terminals TH1 through TH14 of the host device 11 and input/output terminals TD1 through TD14 of the display device 12.
The host device 11 includes an HDMI transmission unit 111 and a graphic control unit 112. The display device 12 includes a serial electrically erasable and programmable read only memory (EEPROM) 122 and an HDMI reception unit 121.
The HDMI transmission unit 111 in the host device 11 converts audio data SAUD, a clock signal SCS, and digital image data SVID into transition minimized differential signaling (TMDS) signals in an HDMI format and outputs the TMDS signals to the display device 12.
More specifically, the audio data SAUD and the digital image data SVID are processed by the HDMI transmission unit 111 and are output as red signals SR+ and SR− of 2 channels, green signals SG+ and SG− of 2 channels, and blue signals SB+ and SB− of 2 channels. The clock signal SCS is processed by the HDMI transmission unit 111 and is output as clock signals CLK+ and CLK− of 2 channels.
The serial EEPROM 122 in the display device 12 stores extended display identification data (EDID) of the display device 12 and provides the EDID to the graphic control unit 112 of the host device 11 according to an inter-integrated circuit (I2C) communication protocol.
In I2C communication, the graphic control unit 112 exchanges data signals SDA with the serial EEPROM 122 while transmitting a clock signal SCL to the serial EEPROM 122. The graphic control unit 112 provides a power-supply potential of +5V and a ground potential GND to the serial EEPROM 122 for an operation of the serial EEPROM 122. The display device 12 applies a hot plug detect (HPD) signal voltage HPD to the graphic control unit 112 and thus the graphic control unit 112 recognizes that the graphic control unit 112 is connected with the display device 12. Reserved terminals TH14 and TD14 that are not used are referred to as no-connection (NC) terminals.
The graphic control unit 112 in the host device 11 controls an operation of the HDMI transmission unit 111 according to the EDID.
The HDMI reception unit 121 in the display device 12 restores the audio data SAUD, the clock signal SCS, and the digital image data SVID from the TMDS signals in the HDMI format, which have been received from the host device 11.
FIG. 2 illustrates a digital image system in a general digital visual interface (DVI) format. In FIGS. 1 and 2, like reference numerals refer to like elements. Hereinafter, only differences between the digital image system illustrated in FIG. 2 and the digital image system illustrated in FIG. 1 will be described. Referring to FIG. 1, the digital image system in a basic DVI format includes a host device 21, a display device 22, and electric cables. The electric cables are connected between input/output terminals TH1 through TH14 of the host device 21 and input/output terminals TD1 through TD14 of the display device 22.
The host device 21 includes a TMDS transmission unit 211 and a graphic control unit 212. The display device 22 includes a serial EEPROM 222 and a TMDS reception unit 221.
The TMDS transmission unit 211 in the host device 11 converts a clock signal SCS and digital image data SVID into TMDS signals in a DVI format and outputs the TMDS signals to the display device 22.
The serial EEPROM 222 in the display device 22 stores EDID of the display device 22 and provides the EDID to the graphic control unit 212 of the host device 21 according to the I2C communication protocol.
The graphic control unit 212 of the host device 21 controls an operation of the TMDS transmission unit 211 according to the EDID.
The TMDS reception unit 221 in the display device 22 restores the clock signal SCS and the digital image data SVID from the TMDS signals in the DVI format, which have been received from the host device 21.
In the digital image system illustrated in FIG. 1 or 2, the maximum length between the host device 11 or 21 and the display device 12 or 22 is limited to about 10 m. When a distance between the host device 11 or 21 and the display device 12 or 22 is long, a transmission/reception reinforcement device such as an optical cable module, a repeater, or an equalizer is required.
In a digital image system where the host device 11 or 21 transmits digital image data to the display device 12 or 22 using the transmission/reception reinforcement device, transmission of the digital image data is not smooth if an external power supply of the transmission/reception reinforcement device drops and the transmission may not be performed at all if the external power supply is interrupted.